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Historical studies of human interaction with climate are one approach through which to understand responses to environmental stress today. Most studies of vulnerability are based upon short timeframes in the recent past and so may focus on its symptoms rather than its underlying causes, or derive exclusively from systems-based approaches that can present historical change without recourse to human agency. This paper makes extensive use of the historical written record to analyse the comparative root-causes of the vulnerability and resilience of rural farming communities to drought over a period of three centuries (1505–1830) in the area between the Zambezi and Save rivers in southern Africa. The paper first considers vulnerability, resilience and adaptation as temporal frameworks, and analyses evidence for drought and its impacts in the pre-colonial past. It then reconstructs agro-ecosystem, livelihood and institutional vulnerability for six societies and settlements over the long-run using an indicator approach. The resultant trajectories of vulnerability are discussed in the context of the differential impacts of past drought, through which the decisive drivers and constraints of vulnerability and resilience are identified. The paper concludes with a number of key themes from this long-run analysis for contemporary vulnerability and adaptation to climate change, and points to the importance of institutional adaptation, normative goals, and uneven distributions of power. [ABSTRACT FROM AUTHOR]

The role of the land surface in climate and weather has been a major research focus since the 1970s. Since that time our understanding of the issue has greatly changed and many new themes in several disciplines are being considered. This article summarizes the changes in our understanding that have taken place in research on this topic and reviews principally papers that have appeared in the last two decades. Several other papers provide comprehensive reviews of literature that appeared prior to that time. The major changes that have occurred include 1) more sophisticated and rigorous analysis of desertification, 2) increased emphasis on hydrological processes, including the role of groundwater, 3) use of multi-model ensembles and regional models, 4) the emergence of the domain of ecohydrology, with emphasis on detailed feedbacks between water availability and vegetation, 5) examination of the hypothesis that vegetation feedback can produce abrupt climate change, 6) emphasis on the impacts on convective or synoptic-scale systems, and 7) consideration of the impact of aerosols, including the Saharan Air Layer. With the exception of desertification, each of these topics is reviewed. [ABSTRACT FROM AUTHOR]

Abstract The field of quantitative palaeoclimatology has made significant progress in the past decades. However, this progress has been spatially heterogeneous and strong discrepancies – both in terms of quality and density – exist between Europe and North America and the rest of the world. The need to balance this distribution of quantified records has never been stronger, and improving our understanding of past global climate is urgent in order to better evaluate and employ the predictions of climate models. In this paper, it is argued that this gap can be reduced by applying the climate reconstruction method CREST (Climate REconstruction SofTware) calibrated using the open-access GBIF (Global Biodiversity Information Facility) database, which contains hundreds of thousands modern distributions of numerous bio-indicator proxies (e.g. pollen, chironomids, foraminifers, etc.). Using the taxonomical diversity of the GBIF database, CREST can be used to reconstruct various climate and/or environmental parameters from assemblage variety of different records. Independent from the usual reconstruction techniques using surface samples for calibration, the CREST/GBIF framework can also be used as an independent tool that can be easily and efficiently applied (1) to complete the global coverage of climate reconstructions, as exemplified with a precipitation reconstruction from Lake Van, Turkey, (2) to revisit existing data sets to obtain new quantitative reconstructions, and (3) to evaluate and/or refine reconstructions based on other methods. The application of this tool promises to foster advances in our understanding of the past climate variability of the Earth system at a global scale. Highlights • A new, globally applicable probabilistic tool to quantitively reconstruct past climates. • The calibration dataset contains the distributions of multiple palaeoclimatic bio-indicators. • Understudied regions can now be explored using the CREST/GBIF framework. • A dedicated software exists to facilitate the use of the CREST/GBIF framework. [ABSTRACT FROM AUTHOR]

Policy makers have made repeated calls for integration of human and natural sciences in the field of climate change. Serious multidisciplinary attempts began already in the 1950s. Progress has certainly been made in understanding the role of humans in the planetary system. New perspectives have clarified policy advice, and three insights are singled out in the paper: the critique of historicism, the distinction between benign and wicked problems, and the cultural critique of the ‘myths of nature’. Nevertheless, analysis of the IPCC Assessment Reports indicates that integration is skewed towards a particular dimension of human sciences (economics) and major insights from cultural theory and historical analysis have not made it into climate science. A number of relevant disciplines are almost absent in the composition of authorship. Nevertheless, selective assumptions and arguments are made about e.g. historical findings in key documents. In conclusion, we suggest to seek remedies for the lack of historical scholarship in the IPCC reports. More effort at science-policy exchange is needed, and an Integrated Platform to channel humanities and social science expertise for climate change research might be one promising way. [ABSTRACT FROM AUTHOR]

Disturbances are a major determinant of forest carbon stocks and uptake. They generally reduce land carbon stocks but also initiate a regrowth legacy that contributes substantially to the contemporary rate of carbon stock increase in US forestlands. As managers and policy makers increasingly look to forests for climate protection and mitigation, and because of increasing concern about changes in disturbance intensity and frequency, there is a need for synthesis and integration of current understanding about the role of disturbances and other processes in governing forest carbon cycle dynamics, and the likely future of this and other sinks for atmospheric carbon. This paper aims to address that need by providing a quantitative review of the distribution, extent and carbon impacts of the major disturbances active in the US. We also review recent trends in disturbances, climate, and other global environmental changes and consider their individual and collective contributions to the US carbon budget now and in the likely future. Lastly, we identify some key challenges and opportunities for future research needed to improve current understanding, advance predictive capabilities, and inform forest management in the face of these pressures. Harvest is found to be the most extensive disturbance both in terms of area and carbon impacts, followed by fire, windthrow and bark beetles, and lastly droughts. Collectively these lead to the gross loss of about 200 Tg C y − 1 in live biomass annually across the conterminous US. At the same time, the net change in forest carbon stocks is positive (190 Tg C y − 1 ), indicating not only forest resilience but also an apparently large response to growth enhancements such as fertilization by CO 2 and nitrogen. Uncertainty about disturbance legacies, disturbance interactions, likely trends, and global change factors make the future of the US forest carbon sink unclear. While there is scope for management to enhance carbon sinks in US forests, tradeoffs with other values and uses are likely to significantly limit practical implementation. Continued and expanded remote sensing and field-based monitoring capabilities and manipulative experimentation are needed to improve understanding of the US forest carbon sink, and assess how disturbance processes are responding to the pressures of global environmental change. In addition, continued development and application of holistic, decision support tools that consider a range of forest values are needed to enable managers and policy makers to use the best available information for guiding forest resources now and into the future. [ABSTRACT FROM AUTHOR]

This paper summarizes current knowledge about the postglacial history of the vegetation of the Canadian Arctic Archipelago (CAA) and Greenland. Available pollen data were used to understand the initial migration of taxa across the Arctic, how the plant biodiversity responded to Holocene climate variability, and how past climate variability affected primary production of the vegetation. Current evidence suggests that most of the flora arrived in the area during the Holocene from Europe or refugia south or west of the region immediately after local deglaciation, indicating rapid dispersal of propagules to the region from distant sources. There is some evidence of shrub species arriving later in Greenland, but it is not clear if this is dispersal limited or a response to past climates. Subsequent climate variability had little effect on biodiversity across the CAA, with some evidence of local extinctions in areas of Greenland in the late Holocene. The most significant impact of climate changes is on vegetation density and/or plant production. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a first assessment of the global effects of climate-induced sea-level rise on the erosion of sandy beaches, and its consequent impacts in the form of land loss and forced migration of people. We consider direct erosion on open sandy coasts and indirect erosion near selected tidal inlets and estuaries, using six global mean sea-level scenarios (in the range of 0.2–0.8m) and six SRES socio-economic development scenarios for the 21st century. Impacts are assessed both without and with adaptation in the form of shore and beach nourishment, based on cost-benefit analysis that includes the benefits of maintaining sandy beaches for tourism. Without nourishment, global land loss would amount to about 6000–17,000km2 during the 21st century, leading to 1.6–5.3million people being forced to migrate and migration costs of US$ 300–1000billion (not discounted). Optimal beach and shore nourishment would cost about US$ 65–220billion (not discounted) during the 21st century and would reduce land loss by 8–14%, forced migration by 56–68% and the cost of forced migration by 77–84% (not discounted). The global share of erodible coast that is nourished increases from about 4% in 2000 to 18–33% in 2100, with beach nourishment being 3–4 times more frequent than shore nourishment, reflecting the importance of tourism benefits. In absolute terms, with or without nourishment, large countries with long shorelines appear to have the largest costs, but in relative terms, small island states appear most impacted by erosion. Considerable uncertainty remains due to the limited availability of basic coastal geomorphological data and models on a global scale. Future work should also further explore the effects of beach tourism, including considering sub-national distributions of beach tourists. [Copyright &y& Elsevier]

Abstract: Wave climate is highly variable on the world''s coast and its temporal changes and extremes usually imply consequences like erosion or impacts to infrastructures. Alterations in wave climate were little addressed in the four IPCC reports although variations in wave climate may cause extensive coastal impacts. Changes are also often related to climate pattern variability. This variability as well as long-term trends has been an issue of research in recent years. In the region of Latin America and the Caribbean (LAC) an understanding of wave climate and its variability is scant. In this paper we use an extensively calibrated and validated wave reanalysis to describe the wave climatology in the region at different time scales and for scalar and directional wave parameters. Long-term changes are identified in the wave heights and mean direction of the energy flux shows high spatial variability. Correlation patterns of the mean significant wave height and direction of mean energy flux lead to the detection of prominent modes of influence of several climate indices. A wave climate type approach is also used to identify wave variability along the region that allows an identification of different wave climate types in terms of wave parameters and occurrence frequency. In line with the results, the influence of El Niño events shows a higher frequency of occurrence of certain sea-states with respect to non ENSO years. We also explore how climate change affecting storm patterns may be translated into a modification of sea-state occurrence and therefore implying different consequences for coastal zones depending on local wave propagation. [Copyright &y& Elsevier]

Abstract: This paper presents the development of a system dynamic model to simulate and analyze desertification. The human–environment coupled model integrates socio-economic drivers with bio-physical drivers of biomass production, land degradation and desertification. It is based on the UN and GEF definitions of desertification. It illustrates the concept of desertification through differential equation and simulation output graphics. It is supplemented with a causal loop diagram demonstrating the existing feed-back mechanisms. The model relates population pressure and dynamics over time to the growth and availability of biomass resources. The human population stock is described as a function of growth rate, death rate and resources dependent in and out migration of people. The relative growth rate of the stock of resources is modeled as a function of climate and exploitation pressure affecting soil erosion and water availability. The model is applied for the Sahelian desertification syndrome using input data to illustrate and simulate a 150 years period (1900–2050) in Kordofan, Sudan. The model indicates that it is difficult to generate irreversible desertification. [Copyright &y& Elsevier]

Abstract: A method for surface modeling of land cover change (SMLC) is developed on the basis of establishing transition probability matrixes between land cover types and HLZ types. SMLC is used to simulate land cover scenarios of China for the years 2039, 2069 and 2099, for which HLZ scenarios are first simulated in terms of HadCM3 climatic scenarios that are downscaled in zonal model of spatial climate change in China. This paper also analyzes spatial distribution of land cover types, area change and mean center shift of each land cover type, ecotope diversity, and patch connectivity under the land cover scenarios. The results show that cultivated land would decrease and woodland would expand greatly with climatic change, which coincides with consequences expected by implementation of Grain-for-Green policy. Nival area would shrink, and desertification area would expand at a comparatively slow rate in future 100 years. Climate change would generally cause less ecotope diversity and more patch connectivity. Ecosystems in China would have a pattern of beneficial cycle after efficient ecological conservation and restoration. However, if human activities would exceed regulation capacity of ecosystems themselves, the ecosystems in China might deteriorate more seriously. [Copyright &y& Elsevier]

Abstract: The debate on the enhanced greenhouse effect continues, confusing the climate change impact analysis and the decision makers. Hence, this paper is addressed to the extreme regional-scale evaluation of global climate model (GCM). Given that assessment of models is crucial to consider future scenarios in climate change impact analyses, the exploratory work is essential, as it identifies the strengths and weaknesses of GCM to regional-scale differences in model performance, providing insights on regional-scale climate interactions and processes. That is why this manuscript attempts to compare the spatial pattern of a longer temporal aggregation period (1960/61–1989/90) for extreme temperatures simulated by a particular GCM (HadCM3) to that of NCEP Reanalyses, which are considered as “truth”. Climatic risk analyses and forecasting, concern among other topics, assess an interpretation in intensity and frequency of recurrence of long duration extreme values (heat/cold waves). One study assesses the impact of extreme events analysing the temporal dependence of extreme events. The present study leads to the conclusion that the HadCM3 Simulations do not reproduce reasonably the NCEP Reanalyses over the Modelling the Impact of Climate Extremes (MICE—EU Project) domain, even despite the fact that the climatology of extremes has demonstrated very similar spatial patterns. Consequently, all diagnostics of extremes led support to the fitted Generalised Extreme Value (GEV) model for extrapolation, suggesting that the HadCM3 is not adequate for forecasting, simulating future scenarios of extremes based on the analysis of risk or probability maps for spatial uncertainties. The greatest difference between the two models is in terms of the precision of estimation. [Copyright &y& Elsevier]

Abstract: This short introductory paper illustrates some key issues concerning extremes by focusing on daily temperature extremes defined using quantiles and threshold exceedances. The examples include both a low- and a high-elevation site in the Swiss Alps where long records of homogenous daily data are readily available. The analysis of extremes highlights several features, some of them taken from the 2003 heat wave that affected Europe, in particular significant changes in the trends of quantiles in the course of the 20th century, differences in the altitudinal behavior of maximum or minimum temperatures, and close links between means and the extreme quantiles of daily temperatures. [Copyright &y& Elsevier]

This paper investigates the response of the Antarctic ice sheet shape and volume to changes in outlet flow boundary conditions. We model the transmission of outlet flow boundary perturbations toward the inland ice sheet by taking into account the dynamical properties of the profile. We investigate the effect of outlet perturbations according to their time scales. We derive the analytical relation between the temporal wavelength of the perturbations and the induced wavelength of surface undulations. We show that the inland undulation wavelength and transmission increase with the temporal wavelength of the perturbation, so that the short time scale perturbations are strongly filtered. For a given outlet perturbation, the induced frequency depends on the distance to the coast and on the dynamical characteristics of the profile, so that two adjacent flow lines may have different signals. Because outlet perturbations are poorly quantified, it is difficult to predict their impact on sea level change. However, the impact seems to be smaller than that induced by other random processes, such as accumulation rate fluctuations. Finally, an analysis of the ice sheet topography anomalies suggests that in some places, the actual response to a past outlet perturbation can be suspected. [Copyright &y& Elsevier]

The sulphate glacio-chemical profiles constitute a reliable proxy marker for reconstruction of past volcanic history, assuming a reliable method to distinguish sulphate spikes and to evaluate the flux of individual events is set up. The resulting volcanic event profile is used to reconstruct past event frequencies, and to investigate possible links between volcanism and climatic changes. Volcanic event signatures are useful also in comparing time scales from ice cores drilled at different locations. In this paper, a new method to pick out volcanic signals is proposed. It improves on methods based on the calculation of a threshold using a general mean value plus a multiple of the standard deviation by adding: (1) quantification of nonvolcanic sulphate contributions; (2) sulphate fluxes, instead of concentrations, accounting for accumulation rate changes; (3) data treatment using a log-normal statistic, instead of a Gaussian-type distribution, to take into account the real sulphate distribution; (4) a smoothed curve (weighted fitting) to better understand the residual variability of the sulphate background.This method is used to detect volcanic events throughout the 45 ky time span of the EDC96 ice core, drilled at Dome C on the East Antarctic plateau. A total of 283 volcanic signatures are recovered, with a mean of 6.3 events per millennium. The temporal event frequencies indicate that the last 2000 years were probably characterized by the highest volcanic activity in the period covered by the core and that there is no clear link between number of events recorded and climatic changes. [Copyright &y& Elsevier]

It is well known that there is a vast expanse of grassland on the Tibetan Plateau, China. It is suggested that a major climatic factor limiting production of the grassland ecosystem is the low thermo-conditions on the Tibetan Plateau. An increase in temperature may therefore increase the productivity of grasslands on the Plateau. Monthly mean temperature and monthly precipitation data for recent years on the Tibetan Plateau were analyzed. It is clear that the increase in air temperature on the Plateau is greater than that in the whole China and East Asia. On the other hand, statistics show that the production of livestock or meat in the Tibetan Plateau has increased by one to three times since 1978, which means that there should be an equivalent increase in the consumption of plant biomass from the grassland. How is the “increased biomass” related to human activities and climate changes? This paper tries to clarify the relationship between human activities and climate change and to propose a possible answer by laying emphasis on the importance of grassland protection and CO2 flux monitoring. It is suggested that there is a positive feedback in which degradation of grassland by overgrazing will increase potential evapotranspiration level thereby promoting the climate warming and the degradation process. This feedback should be considered seriously in the future. [Copyright &y& Elsevier]

Climate in northeast Qinghai–Tibetan Plateau is characterised by the alternation of summer and winter monsoon circulation, which is generated by thermodynamic and kinetic effects of the immense plateau. The Plateau Monsoon system during the recent geological past has been investigated through a 44-m loess–paleosol section and a 17-m well to obtain the Plateau Monsoon climate changes during the last glacial–interglacial cycle.Thermoluminescence (TL) and optically stimulated luminescence (OSL) methods, as well as field observations and stratigraphic correlation, are used to date the deposit. Magnetic susceptibility (MS), frequency-dependent magnetic susceptibility (FMS), and calcium carbonate content, which are regarded as proxy indicators of strength of the Plateau Summer Monsoon (PSM), are measured. Measurement of grain size distribution, which is regarded as a proxy index of strength of the Plateau Winter Monsoon (PWM), is also carried out. The results show that changes of the unique Plateau Monsoon system during the past 130 kyr are associated with the glacial and interglacial alternations in the Northern Hemisphere. The PSM was unusually strengthened during a period matching the marine oxygen isotope stage 5e (OIS 5e), but it was weak during the OIS 5a and OIS 5c, and was close to that of the OIS 3. The PWM was significantly depressed during OIS 3, and was as weak as that in the Holocene. The PWM and PSM circulations were not always coupled during the last glacial cycle. Changes of the Plateau Monsoon system did not always parallel the SE Asian monsoon, although linkage between them existed to some extent.There are millennial-scale variations in the Plateau Monsoon system, but this is not further discussed in this paper. [Copyright &y& Elsevier]

This paper is concerned with dendroclimatic research aimed at representing the history of very large-scale temperature changes. It describes recent analyses of the data from a widespread network of tree-ring chronologies, made up of ring width and densitometric measurement data spanning three to six centuries. The network was built over many years from trees selected to maximise their sensitivity to changing temperature. This strategy was adopted so that temperature reconstructions might be achieved at both regional and very large spatial scales. The focus here is on the use of one growth parameter: maximum latewood density (MXD). The detailed nature of the temperature sensitivity of MXD across the whole network has been explored and the dominant common influence of mean April–September temperature on MXD variability is demonstrated. Different approaches to reconstructing past temperature for this season include the production of detailed year-by-year gridded maps and wider regional integrations in the form of subcontinental and quasi-hemispheric-scale histories of temperature variability spanning some six centuries.These ‘hemispheric’ summer series can be compared with other reconstructions of temperature changes for the Northern Hemisphere over the last millennium. The tree-ring-based temperature reconstructions show the clear cooling effect of large explosive volcanic eruptions. They also exhibit greater century-timescale variability than is apparent in the other hemispheric series and suggest that the late 15th and the 16th centuries were cooler than indicated by some other data.However, in many tree-ring chronologies, we do not observe the expected rate of ring density increases that would be compatible with observed late 20th century warming. This changing climate sensitivity may be the result of other environmental factors that have, since the 1950s, increasingly acted to reduce tree-ring density below the level expected on the basis of summer temperature changes. This prevents us from claiming unprecedented hemispheric warming during recent decades on the basis of these tree-ring density data alone. Here we show very preliminary results of an investigation of the links between recent changes in MXD and ozone (the latter assumed to be associated with the incidence of UV radiation at the ground). [Copyright &y& Elsevier]

A major obstacle to our ability to assess future impacts of climate and human activities on the global sediment system is the lack of suitable timescales over which long-term processes and system properties may be observed. A long-term view offers the opportunity to observe pre-impact states, trajectories and the history of responses to forcings. The paper explores the scope of sediment archives in lakes and the continental margin as sources of information to inform about spatio-temporal characteristics of total suspended sediment (TSS) flux across spatial scales ranging from small catchments (<103 km2) to regional–continental basins (103–106 km2), and over timescales varying from decades to millennia. Numerous published studies, representing many geographical regions, provide estimates for sedimentation rates over full- or part-Holocene timescales, based largely on 14C and 210Pb dating. Results from small–medium drainage basins show that, during the Holocene, climate has been largely subordinate to human impact in controlling long-term shifts in sediment loads, though the evidence for short-term climate impacts is also clear. The rise in sediment delivery following major human impact is typically 5–10-fold higher than under undisturbed conditions, but may be higher depending upon the environment and intensity of impact. Sediment-source studies suggest that surface soil rarely dominates the sediment load, and that channel and gully sources often dominate even in small basins. For larger drainage basins, the forcing–response mechanisms are less clear and there is evidence to suggest that values for modern fluxes lie close to long-term averages. A more systematic analysis of the relative magnitude of change in sediment flux in different basin sizes reveals a global trend where relative changes diminish with increasing basin size. The findings suggest that small basins are most responsive to impacts and will show the largest changes in sediment flux. In contrast, large basins with effective storage zones and very slow reaction times lead to far weaker levels of spatio-temporal coupling. One implication is that the most rapid increases in sediment flux to the coast are caused by disturbance in small–medium drainage basins feeding directly to the coast. Overall, lake and marine sediment archives provide a range of useful information, often with high temporal resolution, that is difficult to obtain by other means. Future studies may be able to use these datasets to provide a typological classification of sediment regimes according to different spatio-temporal characteristics of their forcing–response mechanisms. [Copyright &y& Elsevier]

In this paper, we examine the orbital signal in Earth''s climate with a coupled model of intermediate complexity (ECBilt). The orbital influence on climate is studied by isolating the obliquity and precession signal in several time-slice experiments. Focus is on monsoonal systems with emphasis on the African summer monsoon. The model shows that both the precession and the obliquity signal in the African summer monsoon consists of an intensified precipitation maximum and further northward extension during minimum precession and maximum obliquity than during maximum precession and minimum obliquity. In contrast to obliquity, precession also influences the seasonal timing of the occurrence of the maximum precipitation. The response of the African monsoon to orbital-induced insolation forcing can be divided into a response to insolation forcing at high northern latitudes and a response to insolation forcing at low latitudes, whereby the former dominates. The results also indicate that the amplitude of the precipitation response to obliquity depends on precession, while the precipitation response to precession is independent of obliquity. Our model experiments provide an explanation for the precession and obliquity signals in sedimentary records of the Mediterranean (e.g., Lourens et al. [Paleoceanography 11 (1996) 391, Nature 409 (2001) 1029]), through monsoon-induced variations in Nile river outflow and northern Africa aridity. [Copyright &y& Elsevier]

The balance of the world carbon exchanges shows a 1.3 GtC/year unknown sink in the continental biosphere. The aim of this article is to determine the contribution of the karstic dissolution processes to this sink. To calculate the karstic dissolution in every part of the world, a new parameter has been created, called «maximal potential dissolution» (MPD). It calculates the theoretical dissolution rate in an idealized karstic system reduced to a simple, pure carbonated block crossed by a flux of CO2-enriched water. MPD is as efficient as other methods in calculating the karstic dissolution. MPD can be calculated everywhere with the mean annual temperature and precipitation values. In this paper, climatic data from 266 meteorological stations all over the world have been treated. They gave a mean MPD value for each main climatic type. The calculation has been made from 10° square grids, each grid assigned to a climatic type, i.e. to a mean value of MPD. The total consumed carbon mass all around the world is thus around 0.3 GtC/year, which represents 23% of the unknown carbon sink. More precise calculations are in progress based on a thousand climatic values. [Copyright &y& Elsevier]

This paper addresses two questions: how do radiative contributions to global climate model feedbacks vary geographically, and hence which regions and physical processes are most important in determining final climate sensitivity in a General Circulation Model (GCM)? Offline radiation calculations were used to evaluate in detail the strength and spatial distribution of top of atmosphere (TOA) radiative perturbations for the BMRC GCM under a doubling of CO2. The long wave and short wave radiative perturbations were considered separately. The net global effect of these radiative perturbations determines the strength of the global model feedbacks, and hence the climate sensitivity. The geographical distribution of the radiative perturbations on the other hand helps to identify the model processes that are most important for determining the strength of model feedbacks. This study found that globally, the dominant positive feedbacks were for (a) water vapour amount and height, and cloud height for long wave radiation and (b) albedo and cloud amount for short wave radiation. The dominant negative feedback (apart from the surface temperature term itself) occurred for cloud amount changes in the long wave. Geographically, the contributions to the water vapour feedback strength varied markedly by location, with subtropical, and upper tropospheric regions contributing relatively strongly to the net global feedback. The water vapour height component correlated quite strongly with convective changes while the amount term was correlated with fractional precipitable water changes. The contribution of different precipitable water regimes in the tropics to global water vapour feedback was assessed—relatively dry areas contributed disproportionately, but did not dominate the overall feedback because of their small areas. Contributions to cloud amount and height feedbacks in the long wave were found to be uncorrelated in space, indicating their different controlling processes. The long wave amount component correlated strongly with upper cloud, and convective changes. The short wave component of the cloud feedback depended on cloud changes at all levels, producing its strongest contribution to feedbacks in mid latitudes, where the sign of cloud changes agreed at different heights. The effect of cloud cover on non-cloud feedbacks was also investigated. This study found that clouds weaken all feedbacks, except that of lapse rate, with the greatest impact being on the surface albedo and water vapour amount. The radiative perturbation analysis method presented here proves to be a powerful tool for identifying important physical processes that determine final climate model sensitivity. [Copyright &y& Elsevier]

In this paper, we use molecular paleothermometry, based on the TEX 86 proxy derived from fossilized archaeal lipids, to reconstruct absolute sea surface temperatures (SSTs) for the northwest Tethys Shelf during the late Pliensbachian to early Toarcian (Early Jurassic, ~183 Ma) stages. Our composite record from outcrops in Spain and Italy reveals that tropical SSTs varied between 22 and 32 °C over a ~ 3 Myr time period, including transient temperature excursions of 5–10 °C magnitude with lapse rates of ~0.1 °C/kyr. Changes in reconstructed SSTs covaried with sea level fluctuations and δ18O isotope signatures of marine biocalcifiers, recording recurrent shifts between icehouse and greenhouse states. Parallel trends of reconstructed SST and δ13C isotopes of atmospheric CO 2 may reflect storage of isotopically light carbon in cryosphere reservoirs during icehouse phases and release during greenhouse phases. The existence of a labile cryosphere is considered a prerequisite to explain the inferred rapid climate fluctuations and as a reservoir to facilitate pronounced carbon isotope excursions. • First Toarcian SST record based on molecular paleothermometry. • Highly variable SSTs attest to contrasting climate modes. • Direct coupling between SST, oxygen isotopes and sea level evolution. • Perception of an overall warm early Jurassic Greenhouse world should be discarded. [ABSTRACT FROM AUTHOR]

Despite the progress in sustainable development strategies, the role of the Amazon rainforest as a carbon sink faces increasing disturbances that may have a critical impact on global climate. Understanding the vulnerability of the Amazon rainforest to climate change is a major challenge, considering the complex interaction between human and natural systems. This paper aims, via an interdisciplinary approach, to assess the observed evolution and possible future of the Amazon rainforest, considering different global climate and socio-economic scenarios. By comparing historical with plausible future developments, we present key knowledge to inform mitigation and regional adaptation policy considerations. As an entry point, historical trends of annual mean temperature and precipitation were analysed. In a second step, the same assessment was made for the mean annual NDVI sum (a proxy of yearly plant productivity), representing vegetation strength. For these purposes, a 34-year period (1982–2015) was considered. Trends were analysed based on non-parametric Mann-Kendall and Sen's methods. With this representation of the past, the next step focused on future scenarios. The most plausible global emission pathways were evaluated via the comparison of ten assessments of the possible effects of the mitigation action plans of national governments, as stated in the National Determined Contributions (NDCs). Results indicate a strong consensus that if either current policies, unconditional or conditional NDCs are fulfilled, the limit of global warming by "well below 2 °C" will be exceeded. In this context, climate projections for the Amazon suggest, among other results, an increase in the range of 1.3 °C (lower limit under SSP1-2.6) to 6.5 °C (upper limit under SSP5-8.5). Unlike temperature, positive and negative anomalies are expected for precipitation depending on location. Despite the uncertainty regarding the projections, possible changes such as forest diebacks and savannization may take place, namely in southeastern Amazon, by the end of the century. Overall, this study highlights the importance of carefully considering the combination of different factors, such as deforestation, to guarantee rainforest resilience under climate-driven changes. • Annual trends for 1982-2015 suggest significant temperature increases of 0.2–0.3 °C/decade, generally spread over the Amazon • Strong consensus that if policies, or conditional NDCs are fulfilled, the limit of global warming by "well below 2 °C" will be exceeded • Projections indicate average increases for the Amazon of 4–6.5 °C (SSP5-8.5), 2.2–3.5 °C (SSP2-4.5), and 1.3–2.2 °C (SSP1-2.6) • Southeastern Amazon is the most vulnerable area with increasing temperature, decreasing precipitation, and heavy deforestation [ABSTRACT FROM AUTHOR]

The Atacama Desert in northern Chile is the driest place on Earth. In this region, climate models are subject to large biases, especially precipitation is significantly overestimated. Meteorological observations in the region are sparse and limited to inhabited places at the coast or the foothills of the Andes. To fill this gap, a new network of 15 automatic weather stations has been established beginning April 2017. These stations do not only record standard meteorological parameters such as temperature, humidity and wind, but also soil temperatures and humidity, additionally a wetness sensor gives information about the occurrence of fog. Data from the first year(s) of this network show a very regular wind pattern with easterly winds during night and morning and westerly winds from noon to evening. This wind transports moisture from the Pacific Ocean into the desert which forms fog during the night which may account for a moisture supply on the order of the rare precipitation events in the region. A few precipitation events have been observed during the first years. The recorded data allows to distinguish between different sources: convective precipitation above the Altiplano, which in some cases extended to the western slope of the Andes, and troughs extending from mid latitudes to the region, directing moist air from the pacific into the region. Both of these mechanisms brought only some tenths of mm precipitation. In one case the accidental combination of flow over the Andes and a weak cut-off low above the Pacific led to moisture convergence off the coast of northern Chile and initiated a convective system moving south-east ward which brought for the region extreme precipitation of 3-10 mm. • We present a new network of climate stations in the Atacama Desert • 15 Stations have been installed between the coast and 2500m AMSL and between 20°S and 25°S. • Wind measurements of the stations support the existence of the Rutlland circulation cell driven by the Andes. • Fog is a regular occurring phenomenon mainly during night with frequency and duration depending on location. • Precipitation occured on some occasions and is driven by certain synoptic situtations described in the paper. [ABSTRACT FROM AUTHOR]